What should the Host field be? when setting up a CNAME record for a subdomain site?

Let me say that I have a domain name registered under www.ABC.com and that I have hosted my site on a free hosting provider, such as https://mysite.hostingProvider.com.

When setting up the CNAME record configuration on my domain name provider's website I see these fields.

Host: {What should be here, the default name is & # 39; www & # 39;}

Value: mysite.hostingProvider.com

TTL: Automatic

I do not understand what to put in the 'Host' field because the free site is not accessible with www.mysite.hostingProvider.com.